Fixes search domains not being preserved when the resolv.conf file is
reverted to its previous state. This ensures that important domain
search configuration is maintained during DNS configuration changes.
The search domains handling was missing in setResolvConf function,
which is responsible for restoring DNS settings.
Because ctrld needs to query custom client mapping from it.
While at it, also make the error message clearer when initializing ubios
discover failed, by attaching the command output to returned error.
The systemd-networkd-wait-online is only required if systemd-networkd
is managing any interfaces. Otherwise, it will hang and block ctrld from
starting.
See: https://github.com/systemd/systemd/issues/23304
The only reason that forces ctrld to depend on vyatta-dhcpd service on
EdgeOS is allowing ctrld to watch lease files properly, because those
files may not be created at the time client info table initialized.
However, on some EdgeOS version, vyatta-dhcpd could not start with an
empty config file, causing restart loop itself, flooding systemd log,
making the router run out of memory.
To fix this, instead of depending on vyatta-dhcpd, we should just watch
for lease files creation, then adding them to watch list.
While at it, also making ctrld starts after nss-lookup, ensuring we have
a working DNS before starting ctrld.
